[Dominators][CodeGen] Add MachinePostDominatorTree verification

Summary:
This patch implements Machine PostDominator Tree verification and ensures that the verification doesn't fail the in-tree tests.

MPDT verification can be enabled using `verify-machine-dom-info` -- the same flag used by Machine Dominator Tree verification.

Flipping the flag revealed that MachineSink falsely claimed to preserve CFG and MDT/MPDT. This patch fixes that.

Reviewers: arsenm, hliao, rampitec, vpykhtin, grosser

Reviewed By: hliao

Subscribers: wdng, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D68235

llvm-svn: 373341

1 files changed, 5 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/MachineDominators.cpp b/llvm/lib/CodeGen/MachineDominators.cpp
index 1dfba8638c2..b569ca42d68 100644
--- a/llvm/lib/CodeGen/MachineDominators.cpp
+++ b/llvm/lib/CodeGen/MachineDominators.cpp
@@ -18,12 +18,15 @@
 
 using namespace llvm;
 
+namespace llvm {
 // Always verify dominfo if expensive checking is enabled.
 #ifdef EXPENSIVE_CHECKS
-static bool VerifyMachineDomInfo = true;
+bool VerifyMachineDomInfo = true;
 #else
-static bool VerifyMachineDomInfo = false;
+bool VerifyMachineDomInfo = false;
 #endif
+} // namespace llvm
+
 static cl::opt<bool, true> VerifyMachineDomInfoX(
     "verify-machine-dom-info", cl::location(VerifyMachineDomInfo), cl::Hidden,
     cl::desc("Verify machine dominator info (time consuming)"));